Finder for photographic purposes



June 3, 1941.

H. SAUER FINDER FOR PHOTOGRAPHIC PURPOSES Filed Sept. 10, 1938 l2 and i3preferably are positioned at a right angle with respect to each other,but at any rate cross each other and are not parallel. the ocularopening 2 or the finder a plano-ccnvex lens 8 is arranged. In front ofthe annular convex surtace of the lens 6 is mounted an annular polarizerit, whose polarizing plane is parallel to the polarizing plane of thepolarizer 92. The result of this arrangement that a light my llS passingthrough the picture area is 1colarimd by the polarizer 13, passesunobstructed through the biplansr center portion of the ocular lens andreaches the eye A of the observer.

A light ray it which also passes through the polarizer it, but strikesthe annular polarizer 14, however. is absorbed owing to the crossedpolarizing planes of the polarizers i3 and ii.

Only light rays H which are polarized by the frame-like polarizer I2 andstrike the annular polarizer l4, whose polarizing plane is parallel tothat of polarizer I2, can pass through the polarizer M. The light rays Hare then directed by the convex portion of the ocular lens 8 into theeye A of observer and produce in this manner a bright border around thepicture area in the finder.

Fig. 2 is an elevation view of the'field aperture of the finder andillustrates the shape and arrangement of the two polarizing filters l2and I3.

Since the finder arrangement of the present invention absorbs less lightthan a finder with semi-transparent reflective faces, the finder of theinvention is particularly well adapted to be combined with the baserange finder. The combination of such a picture finder with the rangefinder may be accomplished in such a manner that the ocular aperture ofthe'picture finder forms at the same time the ocular aperture of therange finder.

Fig. 3 illustrates such a picture finder and range finder combination,in which the picture finder is constmcted as shown in Figs. 1 and 2 andtherefore similar parts 01' the same are acce tor provided with the samereference characters. It will be noted that one end of the mirror baseQ55, Al oi the range finder-namely the one provided with the angularlypositioned semi-transparent reflecting face 48is arranged between thepclarizers I2, l3 and the ocular lens 8 of the picture finder. Theoptical members for deflecting the measuring rays of the range finderare designated with 49 and 50 and are arranged in an opening iii of thefront wall 52 or the casing i The front wall 52 is also provided withthe field opening 3 in which the polarizers l2 and it of the picturefinder are mourned. Since range finders of this type and their operationare well known a more detailed description is believed not necessary.

The boundary or border marks appearing in the finder may also be usedfor determining the center of the picture or any other desired points ofthe object 'to be photographed. It is for instance possible to employthe finder of the present invention to advantage in target practicingdevices for aerial cameras and the like.

What I claim as my invention is:

A finder for photographic purposes, including a casing provided at oneend with a field opening and at the other end with an ocular opening,

light polarizing means closing said field opening and comprising twopolarizing foils mounted in the same plane with their polarizing planesat a right angle to each other, one of said polarizing foils forming thepicture area or said finder and the other a picture boundary framesurrounding said picturearea, a plane-convex ocular lens at said ocularopening, the center portion of said ocular lens being biplanar for;permitting an observation of the picture appearing in the picture areain natural size, and an annular polarizing filter in front or themarginal convex face of said ocular lens, the polarizing plane of saidannular polarizing filter being parallel with respect to the polarizingplane of the filter forming the picture boundary frame.

HANS SAUER.

